A known variable valve timing control device is disclosed in Japanese Patent Laid-Open Publication No. 2002-227622. The disclosed variable valve timing control device includes a rotor member integrally connected to a camshaft for opening and closing a valve that is rotatably assembled to a cylinder head of an internal combustion engine, and a housing member connected to a crankshaft via a driving force transmitting member and being rotatable relative to the rotor member. The variable valve timing control device also includes vanes each assembled to one of the rotor member and the housing member, fluid chambers each formed between the rotor member and the housing member and divided into an advanced angle chamber and a retarded angle chamber by the vane, and a target plate (sensor wheel) assembled to at least one of the rotor member and the housing member and includes projecting portions for detecting a rotational angle of the rotor member or the housing member by using a sensor provided in the vicinity of the target plate.
According to the above disclosed variable valve timing control device, the rotor member is rotated relative to the housing member by an fluid pressure selectively supplied to or discharged from the advanced angle chamber or the retarded angle chamber for changing the opening and closing timing of an intake valve or an exhaust vale. In addition, the rotational angle of the target plate, i.e. the rotational angle of the camshaft, is detected by a sensor such as an electromagnetic pick-up provided in the vicinity of the projecting portions of the target plate.
In addition, according to the above disclosed variable valve timing control device, when the target plate is press fit to a boss portion of the rotor member, each position of the target plate and the rotor member in the circumferential direction thereof is determined beforehand. At this time, the position of the target plate in the circumferential direction is determined by utilizing the projecting portions of the target plate and then the target plate is press fit to the rotor member. In case of determining the position of the target plate in the circumferential direction by using the projecting portions thereof, a fixing jig for the target plate may have a complicated structure and thus be expensive for assuring the accuracy if a shape of the projecting portion is complicated. In addition, the projecting portion of the target plate may interfere with the fixing jig, thereby causing the deformation of the projecting portion.
Further, according to the disclosed variable valve timing control device, the press fit amount of the target plate to the rotor member is required to be controlled for assuring an appropriate distance between the target plate and the sensor. Thus, an expensive facility for press fit may be required for controlling the press fit amount of the target plate.
Furthermore, according to the disclosed variable valve timing control device, in order to assure a press fit length of an extending portion of the target plate into the rotor member, a thickness of the extending portion in the axial direction is defined larger than that of the projecting portion of the target plate. In this case, a length of the device is increased in the axial direction to thereby avoid the extending portion of the target plate being press fit to the rotor member from interfering with the housing member provided adjacent to the target plate.
Furthermore, a face of the projecting portion of the target plate that faces the sensor may have an inferior detection performance due to shear droop caused by a press molding. Therefore, a wrong detection may occur.
Thus, a need exists for a variable valve timing control device wherein a sensor wheel for detecting a relative rotational phase between a rotor member integrally connected to a camshaft and a crankshaft can be fixed to a rotor member with an accurate relative position relationship therewith at a low cost.